The long-term objective of this project is to examine physiological mechanisms by which hormones maintain differentiated function in prostate cancer cells. We have used parental cultures of hormone-responsive, tumorigenic AXC rat prostate cancer cells to isolate six to eight clonal cell lines from each of three parental cultures. As a result of preliminary selection based on tumorigenicity, nine clonal cell lines (three from each parental culture) are undergoing extensive characterization. These nine clonal cell lines are highly tumorigenic in repeat tests in intact AXC male rats. The three parental cultures (T, cells always maintained on medium containing 10-7 M testosterone; D, cells always maintained on medium containing 10-7 M 5alpha-dihydrotestosterone; and C, cells maintained on medium lacking steroid supplementation) have given rise to clones of significantly different morphology and indicated hormonal sensitivity. Moreover, tumors produced by these three families of clonal cell lines are morphologically different. Androgen receptor content is highest in T-clonal cell lines, next highest in C-clonal cell lines, and essentially undetectable in D-clonal cell lines. Biochemical, cytological, and morphological characterization of these cells as well as determination of their response to modification of hormone environment are in progress.